Production method of high purity organic compound

ABSTRACT

There is provided a method for obtaining a target organic compound such as an alkyladamantyl ester efficiently by purifying a crude organic compound which contains, as impurities, sublimable materials which start to sublime at temperatures lower than a boiling point of the target organic compound by use of such a simple method as distillation during its production process, without being adversely affected by adherence of the sublimable materials. 
     The distillation is carried out in the presence of a compound having a boiling point which is lower than a boiling point of the target organic compound, e.g., a carbonyl-group-containing compound. For example, 2-methyl-2-adamantyl methacrylate (boiling point: 92° C./0.3 mmHg) containing sublimable impurities such as adamantane (sublimation starting temperature: room temperature or lower) is distilled in the presence of 1,3-dimethyl-2-imidazolidinone (boiling point: 225° C.).

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP01/00542 which has an Internationalfiling date of Jan. 26, 2001, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a method for producing a high purityorganic compound. More specifically, it relates to a method forproducing a high purity organic compound by distilling and purifying acrude organic compound containing sublimable materials as impuritiesefficiently.

BACKGROUND ART

Heretofore, when a high boiling compound containing sublimable materialsas impurities is distilled and purified, there exist a possibility thatthe sublimable materials block a pipe by subliming and a problem thatsolid sublimable materials adhered to the pipe dissolves in a highboiling compound to be distilled out, thereby inhibiting an increase inpurity of the high boiling compound. Thus, it has been difficult todistill and purify a high boiling compound containing sublimablematerials as impurities.

Meanwhile, demand for products of higher purity has been increasingevery year. In particular, a reduction in metal components of a productused in a semiconductor production process is strongly demanded. As apurification method which can remove such metal components efficiently,purification by distillation is suitable.

In recent years, it has been reported that alkyladamantyl(meth)acrylatepolymers have high dry etching resistance in a semiconductor productionprocess (refer to JP-A 5-265212), and a possibility of their use as aresist material for a semiconductor has been receiving attention. In thecase of these alkyladamantyl(meth)acrylates as well, those havingreduced metal components and high purity are desired for use as a resistmaterial for a semiconductor.

It is known that the alkyladamantyl(meth)acrylate can be generallyproduced by obtaining adamantanone first and then alkyladamantanol fromadamantane as a raw material and then reacting the alkyladamantanol with(meth)acrylic acid, (meth)acrylate, (meth)acrylic anhydride or a(meth)acrylic acid halide. However, since thealkyladamantyl(meth)acrylate which is a target compound is a highboiling compound and adamantane, adamantanone and alkyladamantanolremaining as an unreacted raw material and reaction byproducts aresublimable materials having a sublimation starting temperature(sublimation point) lower than a boiling point of the target compound,it has been difficult to purify the target compound efficiently bydistillation.

It is an object of the present invention to provide a method forproducing a target compound of high purity by applying an efficientpurification method to a crude organic compound containing sublimablematerials as impurities for which an efficient distillation/purificationmethod has not been known.

The present inventor has made intensive studies to solve the aboveproblem. As a result, he has found that a target organic compound can beefficiently purified by distilling a crude organic compound in thepresence of a compound having a boiling point lower than that of thetarget organic compound. The present invention has been completed by thefinding.

DISCLOSURE OF THE INVENTION

To be more specific, the present invention is a method for producing ahigh purity organic compound by distilling a crude organic compoundcontaining, as impurities, sublimable materials which sublime attemperatures lower than a boiling point of the target organic compound.It comprises the steps of distilling out a compound having a boilingpoint lower than that of the organic compound by carrying out thedistillation in the presence of the compound having a boiling pointlower than that of the organic compound so as to cause the compound torinse out sublimable materials sublimed and adhered to the inside of adistillation device or prevent sublimable materials from adhering to theinside of the distillation device and then distilling out and recoveringthe organic compound.

In the method of the present invention, a crude organic compound(hereinafter also referred to as “compound to be purified”) containingsublimable materials (hereinafter also referred to as “low-temperaturesublimable materials”) which sublime at temperatures lower than aboiling point of a target organic compound is distilled. The compound tobe purified is not particularly limited as long as it is a crude organiccompound containing low-temperature sublimable materials. Illustrativeexamples of the compound to be purified include (i) a reaction solutioncontaining an unreacted raw material which is obtained by synthesizing atarget organic compound through a chemical reaction using a sublimablematerial which sublimes at temperatures lower than a boiling point ofthe organic compound as a raw material, (ii) a crude product obtainedfrom the reaction solution and containing the raw material as animpurity, (iii) a reaction solution containing sublimable materialswhich are produced as byproducts when the organic compound issynthesized through the chemical reaction and sublime at temperatureslower than the boiling point of the organic compound and (iv) a crudeproduct obtained from the reaction solution and containing thebyproducts as impurities.

An example of an organic compound which inevitably contains sublimablesynthesis raw material and reaction byproducts in a synthesis reactionof the organic compound as described above is an alkyladamantyl ester.In a synthesis reaction of the alkyladamantyl ester, a synthesis rawmaterial and byproducts in the synthesis reaction such as adamantane,adamantanone and alkyladamantanol which are sublimable materials areinevitably mixed into the product. The crude organic compound obtainedin such a synthesis reaction is suitable as an object to be distilled inthe present invention.

The above alkyladamantyl ester is preferably a high boiling compoundwhich has a boiling point at normal pressure of not lower than 100° C.or a boiling point under a reduced pressure of 1 mmHg of not lower than40° C. Further, the method of the present invention is particularlysuitable for a case where a difference between a boiling point of suchan organic compound and sublimation starting temperatures oflow-temperature sublimable materials is at least 10° C., particularly 20to 100° C.

For example, an alkyladamantyl ester such asalkyladamantyl(meth)acrylate is produced by obtaining adamantanone firstand then alkyladamantanol from adamantane as a raw material and thenreacting the alkyladamantanol with a (meth)acrylic acid halide. In thiscase, obtained reaction solutions or crude products obtained from thereaction solutions generally contain, as impurities, adamantane,adamantanone and alkyladamantanol which are an unreacted raw materialand reaction byproducts. Although depending on a degree of vacuum at thetime of distillation, these impurities are generally low-temperaturesublimable materials whose sublimation starting temperatures are lowerthan a boiling point of an alkyladamantyl ester which is a targetcompound by 100 to 10° C. As a method of purifying the target compoundfrom such reaction solutions by distillation, the method of the presentinvention can be particularly suitably used.

An alkyladamantyl ester produced by the above method is represented bythe following formula (1):

(wherein R³ is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, and R⁴ is a hydrogen atom or a methyl group).

In the above formula (1), R³ is a hydrogen atom or an alkyl group having1 to 6 carbon atoms, and R⁴ is a hydrogen atom or a methyl group.Specific examples of the alkyl group having 1 to 6 carbon atoms andrepresented by R³ include linear alkyl groups such as a methyl group, anethyl group, a propyl group, a butyl group and a hexyl group; andbranched alkyl groups such as an isopropyl group, a tertiary butyl groupand a neopentyl group. Particularly, among alkyladamantyl estersrepresented by the above formula (1), those represented by the formula(1) wherein R³ is a methyl group, an ethyl group or a butyl group and R⁴is hydrogen or a methyl group are suitable because they are useful asraw materials for resists for semiconductors and particularly because ahigh degree of purification is important.

In the present invention, the compound to be purified may also contain amaterial (hereinafter referred to as “third material”) other than thetarget organic compound and the low-temperature sublimable materials,such as a material without sublimability or a material withsublimability which has a sublimation starting temperature higher thanthe boiling point of the target organic compound. Generally, a compoundwhich can be the third material is a raw material, byproduct or solventused at the time of synthesis of the target organic compound.

Further, although composition of the compound to be purified is notparticularly limited, the composition is suitably such that the contentof the target organic compound is 50 to 99 wt %, particularly 70 to 99wt %, based on a total weight of the target organic compound and thelow-temperature sublimable materials, from the viewpoint of distillationefficiency or the like. Further, when the third material is contained,the content of the third material is suitably not higher than 50 partsby weight, particularly not higher than 30 parts by weight, when theabove total weight is 100 parts by weight.

In the present invention, distillation of the compound to be purified iscarried out in the presence of a compound (hereinafter also referred toas “distillation assistant”) having a boiling point lower than that ofthe target organic compound so as to purify the target organic compound.

The low-temperature sublimable materials sublime in an early stage ofthe distillation and solidify and adhere to the inside of distillationdevices. The distillation assistant is distilled out concurrently with,right before or right after sublimation of the low-temperaturesublimable materials according to its boiling point and exhibits aneffect of washing out the low-temperature sublimable materials adheredto the inside of the distillation devices or inhibiting adherence of thelow-temperature sublimable materials to the inside of the distillationdevices. Therefore, by recovering a distilled-out target organiccompound after the low-temperature sublimable materials are dischargedby the distillation assistant, the target organic compound to beproduced in the present invention can be recovered at a high purity.

The distillation assistant may be any compound having a boiling pointwhich is lower than that of the target organic compound. The boilingpoint of the distillation assistant may be higher than and equal to orlower than the sublimation starting temperatures of the low-temperaturesublimable materials. When the boiling point of the distillationassistant is higher than or equal to the sublimation startingtemperatures of the low-temperature sublimable materials, thedistillation assistant is distilled out concurrently with or aftersublimation of the low-temperature sublimable materials so as to washout the low-temperature sublimable materials adhered to the inside ofthe distillation devices. Even if the boiling point of the distillationassistant is lower than the sublimation starting temperatures of thelow-temperature sublimable materials, the distillation assistant isdistilled out before the sublimation of the low-temperature sublimablematerials so as to prevent the low-temperature sublimable materials fromadhering to the inside of the distillation devices. As a result, thetarget compound can be distilled at a high purity.

The distillation assistant is preferably one capable of dissolving thelow-temperature sublimable materials in order to recover a high purityorganic solvent at a high yield.

When a distillation assistant which is easily separated from the targetorganic compound is used, the distillation assistant can be removedeasily even if the organic compound is distilled out as distillationproceeds and mixed with the distillation assistant, so that the organiccompound can be obtained at a high purity. For example, if awater-soluble distillation assistant is used when the organic compoundis water-insoluble, the organic compound can be obtained easily bywashing a distillate with water. Further, if a water-insolubledistillation assistant is used when the organic compound is easilysoluble in water, an acid solution or an alkali solution, the organiccompound can be obtained easily by dissolving a distillate in water, anacid solution or an alkali solution, removing the distillation assistantby a liquid separating operation or the like, performing aneutralization operation as required, and removing water. In addition,when the organic compound is insoluble in water and stable in acid oralkali, an acid or alkali distillation assistant can be used. In thiscase, the organic compound can be obtained easily by washing adistillate with an alkali or acid solution.

An appropriate distillation assistant is determined according to typesof the organic compound and low-temperature sublimable materialscontained in the compound to be purified. However, a compound containinga carbonyl group can inhibit adherence of the low-temperature sublimablematerials to the inside of the distillation devices efficiently andmakes it possible to obtain the target organic compound at a high purityeven if the content of the organic compound in the compound to bepurified is low.

Specific examples of distillation assistants which can be suitably usedin the present invention include ethers such as n-butylphenyl ether anddihexyl ether; polyalkylene glycols such as diethylene glycol,triethylene glycol, tetraethylene glycol and dipropylene glycol;sulfoxides and sulfolanes such as dimethyl sulfoxide and sulfolane;phosphoric amides such as hexamethylphosphoric triamide; non-cyclic orcyclic ketones such as benzyl isopropyl ketone, isopropyl phenyl ketone,heptanophenon and methylcyclohexanone; aldehydes such as decanal andbenzaldehyde; esters such as diethylene glycol diacetate and phenylacetate; non-cyclic amides such as dimethylformamide, dipropylformamide,N-benzylacetamide, acetanilide, 1-formylpiperidine, 1-acetylpiperidine,N-formylmorpholine and N,N-diethylacetamide; cyclic amides such asε-caprolactam, 2-pyrrolidinone, N-methylpyrrolidinone,1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 2-piperidone,2-pyrrolidone and N-methyl-4-piperidone; non-cyclic ureas such astetraethylurea, 1,3-diethylurea and 1,1-diethylurea; cyclic ureas suchas 1,3-dimethyl-2-imidazolidinone,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, ethyleneurea andtetrahydro-2-pyrimidinone; imides such as phthalimide and succinimide;acid anhydrides such as cyclohexanedicarboxylic anhydride; urethanessuch as methyl carbamate; and lactides. These distillation assistantsmay be used alone or in combination of two or more.

Of these distillation assistants, cyclic ureas or cyclic amidesrepresented by the following formula (2):

(wherein R¹ is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, A is —CH₂— or >N—R² (wherein R² is a hydrogen atom or an alkylgroup having 1 to 6 carbon atoms), and n is an integer of 1 to 6) areparticularly preferable since they exhibit particularly good solubilityto the low-temperature sublimable materials contained in the crudeorganic compound which is the compound to be purified and the targetorganic compound can therefore be obtained at a high purity and highyield.

In the above formula (1), R¹ and R² are independently a hydrogen atom oran alkyl group having 1 to 6 carbon atoms. Illustrative examples of thealkyl group include linear alkyl groups such as a methyl group, an ethylgroup, a propyl group, a butyl group and a hexyl group; and branchedalkyl groups such as an isopropyl group, a tertiary butyl group and aneopentyl group.

Illustrative examples of particularly preferred distillation assistantsinclude cyclic amides such as ε-caprolactam, 2-pyrrolidinone,N-methylpyrrolidinone, 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone,2-piperidone, 2-pyrrolidone and N-methyl-4-piperidone; and cyclic ureassuch as 1,3-dimethyl-2-imidazolidinone,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, ethyleneurea andtetrahydro-2-pyrimidinone.

A manner in which the distillation assistant is caused to be present isnot particularly limited as long as it is a manner in which thedistillation assistant can wash out low-temperature sublimable materialssublimed and adhered to the inside of the distillation devices orprevent adherence of the low-temperature sublimable materials to theinside of the distillation devices before the target organic compoundstarts to boil. For example, the distillation assistant may be mixedwith the compound to be purified in advance prior to start ofdistillation or fed directly into a distiller, a distillation column, adistilling tube or a reflux line after start of distillation.

In addition to the above effect of washing out the low-temperaturesublimable materials, effects of the distillation assistant include, forexample, an effect of facilitating handling of the compound to bepurified by decreasing the viscosity of the compound to be purified orchanging the compound to be purified into a solution or suspension whenthe organic compound is solid at room temperature, through addition ofthe distillation assistant. Further, an effect of achieving suchpurification by distillation that can be carried out efficiently withoutdeposition of solids during distillation operation (particularly duringcooling of a distillate) can also be expected. When these effects areexpected in addition to the above wash-out effect, a liquid having aboiling point close to the boiling point of the organic compound issuitably added to the compound to be purified as a second distillationassistant.

The distillation assistant is added in an amount sufficient to wash outall the low-temperature sublimable materials from the distillationdevices. The amount of the distillation assistant can be determined inconsideration of amounts of the impurities and their solubilities in thedistillation assistant and is preferably 0.1 to 100 parts by weight,more preferably 0.2 to 20 parts by weight, based on 1 part by weight ofthe low-temperature sublimable materials contained in the compound to bepurified.

In the production method of the present invention, a manner in which thedistillation is carried out in the presence of the distillationassistant is not particularly limited, and simple distillation orfractional distillation is used. In the case of the fractionaldistillation, as a fractionating column, a thin-film fractionatingcolumn such as a vigoureux-type fractional column, a concentricfractional column, a spinning band fractional column and a packedfractional column or a plate fractionating column such as a bubble-capfractionating column and a porous plate-type fractionating column issuitably used. When vacuum distillation is performed, a thin-filmfractionating column which undergoes little pressure loss isparticularly suitably used. Further, a known distillation mode such as aKugel roll or thin-film distillation can be used without anylimitations. In addition, distillation conditions including temperature,pressure and a reflux ratio are not particularly limited and may bedetermined as appropriate according to composition of the compound to bepurified, the type and amount of the distillation assistant, purity ofthe organic compound to be obtained at the end, and the like.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to Examples and Comparative Examples. The present invention,however, shall not be limited by these Examples in any way.

Example 1

To 1 part by weight of 2-methyl-2-adamantyl methacrylate with a purityof 72 wt % (boiling point: 92° C./0.3 mmHg) which contained, assublimable impurities, 2.1 wt % of adamantane (sublimation startingtemperature: room temperature or lower), 5.3 wt % of2-methyleneadamantane (sublimation starting temperature: 30° C.), 4.5 wt% of 2-adamantanone (sublimation starting temperature: 50° C.) and 1.2wt % of 2-methyl-2-adamantanol (sublimation starting temperature: 60°C.), 0.05 parts by weight of 1,3-dimethyl-2-imidazolidinone (boilingpoint: 225° C.) was added, and distillation was carried out under areduced pressure.

The distillation was carried out at a degree of vacuum of 0.3 mmHg byuse of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary. Although small amounts ofadamantane and the like which were contained as impurities wereinitially adhered inside the distillation devices, they graduallydissolved and come off after 1,3-dimethyl-2-imidazolidinone had startedto be distilled out. The impurities did not cause a blockage. A firstdistillate was removed, and a main distillate started to be collected ata point where 2-methyl-2-adamantyl methacrylate started to be distilledout. The 2-methyl-2-adamantyl methacrylate did not mix with the1,3-dimethyl-2-imidazolidinone. From the collected main distillate,2-methyl-2-adamantyl methacrylate with a purity of 97.7 wt % could beobtained.

Example 2

Distillation was carried out in accordance with Example 1 except that0.3 parts by weight of N-methylpyrrolidinone (boiling point: 81° C./10mmHg) was used in place of 1,3-dimethyl-2-imidazolidinone used as adistillation assistant in Example 1. Sublimable impurities which hadbeen initially adhered to the insides of distillation devices graduallydissolved and come off after N-methylpyrrolidinone had started to bedistilled out. The impurities did not cause a blockage. In a maindistillate, the N-methylpyrrolidinone was mixed with2-methyl-2-adamantyl methacrylate which was distilled out. However, whenthe distillate was rinsed with pure water, 2-methyl-2-adamantylmethacrylate with a purity of 95.8 wt % could be obtained.

Example 3

To 1 part by weight of 2-ethyl-2-adamantyl methacrylate with a purity of82 wt % (boiling point: 96° C./0.2 mmHg) which contained, as sublimableimpurities, 6.3 wt % of adamantane, 2.1 wt % of 2-adamantanone and 0.9wt % of 2-ethyl-2-adamantanol (sublimation starting temperature: 60°C.), 0.1 parts by weight of tetraethylurea (boiling point: 214° C.) and0.1 parts by weight of1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (boiling point: 232°C.) were added, and distillation was carried out under a reducedpressure.

The reduced-pressure distillation was carried out at a degree of vacuumof 0.2 mmHg by use of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary.

As a result, the distillation proceeded without any solids precipitatedin the distillation devices. After a main distillate was dissolved inhexane and rinsed with pure water, the hexane was removed bydistillation. Thereby, 2-ethyl-2-adamantyl methacrylate with a purity of96.5 wt % could be obtained. When the 2-ethyl-2-adamantyl methacrylatewas left to stand at room temperature, it became crystals.

Example 4

To 1 part by weight of 2-butyl-2-adamantyl methacrylate with a purity of79 wt % (boiling point: 103° C./0.2 mmHg) which contained, as sublimableimpurities, 5.1 wt % of adamantane, 1.1 wt % of 2-adamantanone and 0.4wt % of 2-butyl-2-adamantanol (sublimation starting temperature: 70°C.), 0.1 parts by weight of1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (boiling point: 232°C.) was added, and distillation was carried out under a reduced pressurein the same manner as in Example 3.

As a result, the distillation proceeded without any solids precipitatedin distillation devices. After a main distillate was dissolved in hexaneand rinsed with pure water, the hexane was removed by distillation.Thereby, 2-butyl-2-adamantyl methacrylate with a purity of 97.5 wt %could be obtained.

Example 5

To 1 part by weight of 2-methyl-2-adamantyl methacrylate with a purityof 78 wt % (boiling point: 92° C./0.3 mmHg) which contained, assublimable impurities, 0.05 wt % of adamantane (sublimation startingtemperature: room temperature or lower), 2.5 wt % of 2-adamantanone(sublimation starting temperature: 50° C.) and 3.8 wt % of2-methyl-2-adamantanol (sublimation starting temperature: 60° C.), 0.1parts by weight of diethylene glycol (boiling point: 245° C.) was added,and distillation was carried out under a reduced pressure.

The reduced-pressure distillation was carried out at a degree of vacuumof 0.3 mmHg by use of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary. Although 2-adamantanone and2-methyl-2-adamantanol contained as impurities were initially adhered tointernal walls of the distillation devices by subliming, they graduallydissolved and come off after diethylene glycol had started to bedistilled out. The impurities did not cause a blockage. A firstdistillate was removed, and then a main distillate started to becollected at a point where 2-methyl-2-adamantyl methacrylate started tobe distilled out. The diethylene glycol did not mix with the2-methyl-2-adamantyl methacrylate and formed a separate layer under the2-methyl-2-adamantyl methacrylate. By separating the underlying layerfrom the solution, 2-methyl-2-adamantyl methacrylate with a purity of97.6 wt % could be obtained.

Example 6

Distillation was carried out in accordance with Example 5 except thatN-methylpyrrolidinone (boiling point: 81° C./10 mmHg) was used in placeof diethylene glycol used as a distillation assistant in Example 5.Sublimable impurities which had been initially adhered to the insides ofdistillation devices gradually dissolved and come off afterN-methylpyrrolidinone had started to be distilled out. The impuritiesdid not cause a blockage.

In a main distillate, the N-methylpyrrolidinone was mixed with2-methyl-2-adamantyl methacrylate which was distilled out. However, whenthe distillate was rinsed with pure water, 2-methyl-2-adamantylmethacrylate with a purity of 97.0 wt % could be obtained.

Example 7

To 1 part by weight of 2-ethyl-2-adamantyl methacrylate with a purity of86 wt % (boiling point: 96° C./0.2 mmHg) which contained, as sublimableimpurities, 0.2 wt % of adamantane, 2.0 wt % of 2-adamantanone and 0.8wt % of 2-ethyl-2-adamantanol (sublimation starting temperature: 60°C.), 0.1 parts by weight of diethylene glycol (boiling point: 245° C.)and 0.1 parts by weight of tetraethylene glycol (boiling point: 314° C.)were added, and distillation was carried out under a reduced pressure.

The reduced-pressure distillation was carried out at a degree of vacuumof 0.2 mmHg by use of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary.

As a result, the distillation proceeded without any solids precipitatedin the distillation devices. After a main distillate was dissolved inhexane and rinsed with pure water, the hexane was removed bydistillation. Thereby, 2-ethyl-2-adamantyl methacrylate with a purity of96.3 wt % could be obtained. When the 2-ethyl-2-adamantyl methacrylatewas left to stand at room temperature, it became crystals.

Example 8

To 1 part by weight of 2-butyl-2-adamantyl methacrylate with a purity of85 wt % (boiling point: 103° C./0.2 mmHg) which contained, as sublimableimpurities, 0.1 wt % of adamantane, 1.0 wt % of 2-adamantanone and 0.5wt % of 2-butyl-2-adamantanol (sublimation starting temperature: 70°C.), 0.1 parts by weight of tetraethylene glycol (boiling point: 314°C.) was added, and distillation was carried out under a reduced pressurein the same manner as in Example 7.

As a result, the distillation proceeded without any solids precipitatedin distillation devices. After a main distillate was dissolved in hexaneand rinsed with pure water, the hexane was removed by distillation.Thereby, 2-butyl-2-adamantyl methacrylate with a purity of 97.5 wt %could be obtained.

Example 9

To 1 part by weight of 2-methyl-2-adamantyl methacrylate with a purityof 65 wt % (boiling point: 92° C./0.3 mmHg) which contained, assublimable impurities, 0.1 wt % of adamantane (sublimation startingtemperature: room temperature or lower), 12.4 wt % of2-methyleneadamantane (sublimation starting temperature: 40° C.), 6.3 wt% of 2-adamantanone (sublimation starting temperature: 50° C.) and 2.7wt % of 2-methyl-2-adamantanol (sublimation starting temperature: 60°C.), 0.1 parts by weight of 1,3-dimethyl-2-imidazolidinone (boilingpoint: 225° C.) was added, and distillation was carried out under areduced pressure.

The distillation was carried out at a degree of vacuum of 0.3 mmHg byuse of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary. Although some portions ofadamantane and the like which were contained as impurities wereinitially adhered to walls of the distillation devices by sublimation,they gradually dissolved and come off after1,3-dimethyl-2-imidazolidinone had started to be distilled out. Theimpurities did not cause a blockage. A first distillate was removed, anda main distillate started to be collected at a point where purity of2-methyl-2-adamantyl methacrylate exceeded 80%. From the collected maindistillate, 2-methyl-2-adamantyl methacrylate with a purity of 97.7 wt %could be obtained.

Examples 10 to 19

Distillations were conducted in accordance with Example 9 except thatvarious distillation assistants shown in Table 1 were used in place of1,3-dimethyl-2-imidazolidinone used as a distillation assistant inExample 9. When a main distillate contained a distillation assistant,the main distillate was dissolved in hexane and then rinsed with purewater and then the hexane was removed by distillation so as to obtain atarget product.

The results are also shown in Table 1. Even if a large amount oflow-temperature sublimable materials were contained, adhesion of thelow-temperature sublimable materials could be inhibited effectively whena compound containing a carbonyl group was used as a distillationassistant.

Distillation Assistant Purity of Target Amount Added Product in MainEx.No. Type (Parts by Weight) Distillate (wt %) 101,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone 0.1 98.1 (boilingpoint: 232° C.) 11 1-methyl-2-piperidone (boiling point: 225° C.) 0.198.2 12 2-piperidone (boiling point: 256° C.) 0.1 98.0 131,3-dimethyl-2-imidazolidinone (boiling point: 225° C.) 0.05 97.41-acetylpiperidine (boiling point: 224° C.) 0.05 14 1-formylpiperidine(boiling point: 220° C.) 0.1 95.5 15 isopropyl phenyl ketone (boilingpoint: 226° C.) 0.1 95.3 16 N,N-diethylacetacetamide (boiling point:110° C./10 mmHg) 0.1 94.2 17 diethylene glycol diacetate (boiling point:245° C.) 0.1 95.7 18 diethylene glycol (boiling point: 245° C.) 0.1 91.319 dihexyl ether (boiling point: 226° C.) 0.1 89.7 Ex.: Example

Comparative Example 1

When reduced-pressure distillation was carried out without addinganything to 2-methyl-2-adamantyl methacrylate with a purity of 79 wt %which was used in Example 1, cooling pipes of distillation devices wereblocked by sublimable solids, thereby inhibiting the distillation.

Comparative Example 2

When reduced-pressure distillation was carried out without addinganything to 2-methyl-2-adamantyl methacrylate with a purity of 65 wt %which was used in Example 9, cooling pipes of distillation devices wereblocked by sublimable solids, thereby inhibiting the distillation.

As described above, according to the production method of the presentinvention, sublimable materials which sublime and adhere to pipes andthe like at an initial stage of distillation can be dissolved or comeoff upon sublimation of the sublimable materials or by a distillationassistant which is distilled out after the sublimable materials, therebypreventing the sublimable materials from blocking the pipes and/ordissolving in an organic compound. Further, even if a distillationassistant is mixed into an organic compound, it can be removed easily,thereby making it possible to distill and purify an organic compoundefficiently.

According to the present invention, a high boiling compound which hasheretofore been difficult to distill and purify, i.e., a high boilingcompound containing sublimable materials as impurities, can be distilledand purified easily. In addition, by use of the production method of thepresent invention, a high purity alkyladamantyl ester which isconsidered promising as a resist material for a semiconductor can beobtained easily.

1. A method for producing a high purity alkyladamantyl ester at a purityof 89.7% or higher represented by the following formula (1):

wherein R³ is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms and R⁴ is a hydrogen atom or a methyl group which contains asimpurities, sublimable materials which sublime at temperatures lowerthan a boiling point of the alkyladamantyl ester, comprising the stepsof distilling out a compound having a boiling point lower than that ofthe alkyladamantyl ester by carrying out the distillation in thepresence of the compound having a boiling point lower than that of thealkyladamantyl ester so as to cause the compound to rinse out sublimablematerials sublimed and adhered to the inside of a distillation device orprevent sublimable materials from adhering to the inside of thedistillation device and then distilling out and recovering thealkyladamantyl ester.
 2. The method of claim 1, wherein the sublimablematerials are compounds having sublimation starting temperatures lowerthan the boiling point of the target organic compound by 100 to 10° C.3. The method of claim 1, wherein the sublimable materials areadamantane, adamantanone and alkyladamantanol.
 4. The method of claim 1,wherein the compound having a boiling point lower than that ofalkyladamantyl ester is an ether, polyalkylene glycol, sulfoxide,sulfolane, phosphoric acid amide, non-cyclic or cyclic ketone, aldehyde,ester, non-cyclic or cyclic amide, non-cyclic or cyclic urea, imide,acid anhydride, urethane or lactide.
 5. The method of claim 1, whereinthe compound having a boiling point lower than that of thealkyladamantyl ester is water-soluble, acid solution-soluble or basicsolution-soluble.
 6. The method of claim 1, wherein the compound havinga boiling point lower than that of an alkyladamantyl ester is a cyclicurea or cyclic amide represented by the following formula (2):

wherein R¹ is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, A is —CH₂— or >N—R² wherein R² is a hydrogen atom or an alkylgroup having 1 to 6 carbon atoms, and n is an integer of 1 to
 6. 7. Themethod of claim 1, wherein the compound having a boiling point lowerthan that of the alkyladamantyl ester is present in an amount of 0.1 to100 parts by weight per part by weight of the sublimable material. 8.The method of claim 1, wherein the high purity alkyladamantyl ester isobtained at a purity of 96.5% or higher.
 9. The method of claim 2,wherein the high purity alkyladamantyl ester is obtained at a purity of96.5% or higher.
 10. The method of claim 5, wherein the high purityalkyladamantyl ester is obtained at a purity of 96.5% or higher.